adding exceptional handling for serializing the metadata

Signed-off-by: Francisco Javier Arceo <farceo@redhat.com>

llama_stack/providers/utils/memory/vector_store.py

@@ -144,7 +144,12 @@ def make_overlapped_chunks(
 ) -> list[Chunk]:
     tokenizer = Tokenizer.get_instance()
     tokens = tokenizer.encode(text, bos=False, eos=False)
-    metadata_tokens = tokenizer.encode(str(metadata), bos=False, eos=False)
+    try:
+        metadata_string = str(metadata)
+    except Exception as e:
+        raise ValueError("Failed to serialize metadata to string") from e
+
+    metadata_tokens = tokenizer.encode(metadata_string, bos=False, eos=False)
 
     chunks = []
     for i in range(0, len(tokens), window_len - overlap_len):

tests/unit/rag/test_vector_store.py

@@ -108,3 +108,22 @@ class TestVectorStore:
             assert isinstance(chunk.metadata["token_count"], int)
             assert chunk.metadata["token_count"] > 0
             assert chunk.metadata["metadata_token_count"] == len_metadata_tokens
+
+    def test_raise_overlapped_chunks_metadata_serialization_error(self):
+        document_id = "test_doc_ex"
+        text = "Some text"
+        window_len = 5
+        overlap_len = 2
+
+        class BadMetadata:
+            def __repr__(self):
+                raise TypeError("Cannot convert to string")
+
+        problematic_metadata = {"bad_metadata_example": BadMetadata()}
+
+        with pytest.raises(ValueError) as excinfo:
+            make_overlapped_chunks(document_id, text, window_len, overlap_len, problematic_metadata)
+
+        assert str(excinfo.value) == "Failed to serialize metadata to string"
+        assert isinstance(excinfo.value.__cause__, TypeError)
+        assert str(excinfo.value.__cause__) == "Cannot convert to string"